SKS said it was assuming damages amounted on average to 15 percent of the initial retail price of the vehicles concerned and that, together with insurance companies supporting the legal action, it wanted to give Swiss-based car owners the possibility to enforce their rights without disproportionate financial risk.

“The cars sold as environmentally friendly were overpriced from the beginning. Due to the manipulation of the exhaust system, they then lost even more of their value on the secondary market,” SKS (Stiftung fuer Konsumentenschutz) said in a statement on Friday.

AMAG, which imports the cars into Switzerland, said in a statement on its website it did not understand why SKS filed the claim because prices on the secondary market for VW diesel cars were at least on the same level or even higher than those of competing models.

It also said it had not acted with the intention of wilfully deceiving customers.

Volkswagen could not immediately be reached for comment.

VW admitted in September 2015 to installing secret software in hundreds of thousands of U.S. diesel cars to cheat exhaust emissions tests and make them appear cleaner than they were on the road, and that as many as 11 million vehicles could have similar software installed worldwide.

Earlier this month, Germany’s highest court rejected a bid by Volkswagen to suspend the work of a special auditor appointed to investigate management actions in the emissions scandal.